The present invention relates to a color graphic display device for converting color index information to color information on a screen to perform graphic display and, more particularly, to a color index conversion system for interarea copy.
FIG. 1 shows a conventional graphic display device for performing graphic display by using frame memories 11 through 14. According to this device, for example, color index data B0 through B3 and position data (not shown) on the screen are specified to store pixel data in the frame memories 11 through 14. In this case, the frame editing and read/write operation are performed under the control of a frame editing block 15. Each bit of color index data CI corresponds to one pixel on a display monitor 16. The color index data divided and stored in these frame memories 11 through 14 are read out therefrom and are converted by a display conversion device 17 to a color information on the screen. Color display appears on the display monitor 16 in accordance with this color information. In addition, according to the conventional device, the frame memories 11 through 14 are divided into a plurality of groups (e.g., a group of frame memories 11 and 12, and a group of frame memories 13 and 14). In this case, the frame memories 11 and 12 serve as a display memory independently of a display memory constituted by the frame memories 13 and 14. For this reason, the graphic display by the frame memories 11 and 12 can be superposed on the graphic display by the frame memories 13 and 14 on the display monitor 16.
This conventional device can perform interarea copy processing for copying the contents of areas A of the frame memories 11 and 12 to areas B of the frame memories 13 and 14. This interarea copy operation is controlled by the frame editing block 15 in the following manner. Color index data (RCI) B3B2B1B0 corresponding to the areas A are sequentially read out from the frame memories 11 through 14. The bit data B3B2 of the copy source frame memories 11 and 12 (the frame memories subjected to a real read operation) of the readout color index data B3B2B1B0 are selectively extracted. This extraction operation is performed by the frame editing block 15. Subsequently, the bit data B3B2 are set in bit positions of bit data B1B0 of the copy destination frame memories 13 and 14 (i.e., the frame memories subjected to a real write operation). Next, the color index data xxB3B2, are updated (x represents that the corresponding bit can be logic "1" or "0"). This data updating is also performed by the frame editing block 15. Finally, the updated color index data (xxB3B2) is supplied to the frame memories 11 through 14, and the bit data B3B2 corresponding only to the frame memories 13 and 14 is written therein by the frame editing block 15.
In this manner, according to the conventional color graphic display device, the bit data corresponding to the copy source frame memories is selected from the corresponding color index data when interarea copy is performed. The selected bit data is then set in the bit positions corresponding to the copy destination frame memories so as to update the color index data. These two operations are an obstacle against high-speed copy between the areas. In addition, the firmware of the frame editing block 15 is overloaded.